Optional Element type DTD

Question

i have an XML doc like this:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE school SYSTEM ""> 
<school> 
    <data> 
        <id>
            <uid>1</uid> 
        </id>
        <information>
            <name>Michael</name>
            <surename>Julius</surename>
        </information>
        <note> 
            <test>hans</test>

        </note> 
    </data> 
</school> 

and a DTD File

<!ELEMENT school (data)> 
<!ELEMENT data (id,information,note)> 
<!ELEMENT id (uid)> 
<!ELEMENT uid (#PCDATA)>
<!ELEMENT information (name,surename?)> 
<!ELEMENT name (#PCDATA)> 
<!ELEMENT surename (#PCDATA)> 
<!ELEMENT note (#PCDATA)>  <--- unknown element type

I want to define the <note> element with optional element types like

<note> 
  <test2>test2</test2>
</note>

or

<note>
  <unknown name></unknown name>
</note>

any help? thankz

Answer 1

You can use ANY in the element declaration for note. This will allow any element to be a child of note, but that element also has to be defined (have an element declaration). You can't have an undefined element.

Example note declaration:

<!ELEMENT note ANY>

Example instance (the DTD can be external, but I used an internal subset because it was easier to test):

<!DOCTYPE school [
<!ELEMENT school (data)> 
<!ELEMENT data (id,information,note)> 
<!ELEMENT id (uid)> 
<!ELEMENT uid (#PCDATA)>
<!ELEMENT information (name,surename?)> 
<!ELEMENT name (#PCDATA)> 
<!ELEMENT surename (#PCDATA)> 
<!ELEMENT note ANY>
<!ELEMENT test2 (#PCDATA)><!--The element "test2" still has to be declared.-->
]> 
<school> 
    <data> 
        <id>
            <uid>1</uid> 
        </id>
        <information>
            <name>Michael</name>
            <surename>Julius</surename>
        </information>
        <note> 
            <test2>hans</test2>         
        </note> 
    </data> 
</school>